Every black bear I've ever run across in the woods has run like hell when they saw me. In habituated areas, they're like dogs begging at the kitchen table - but I never treat them as such. Like any person, you never know if they might be having a bad day.
They are tremendously strong and could remove your face with a swat in a heartbeat. They can run like hell too, even though they usually plod along. Don't try to outrun a bear. They are faster than a horse over a short distance.
Grizzly bears, I never spent time out west. I know they aren't as nice as black bears usually tend to be. They say if confronted with an aggressive black bear to yell and make yourself look larger (fan out a coat if wearing one), with Grizzlies, yes, play dead if you are ever in that unfortunate situation. You really aren't going to triumph over either if it comes down to hand to paw combat.